From the time of the downfall of the Sassanid Dynasty in 21/22 AH until the dawn of political independence in Iran in 206 AH, even though Iran did not have its own independent government, the Iranian culture was vibrant, dynamic, and impacting. A large number of theologians who wrote in the Arabic language until the second half of the 4th Century AH/10th Century AD and even after that period belonged to areas that used to be parts of the Sassanid Empire and were, thus, under the influence of the intellectual culture that had existed in Iran under the Sassanid rule. This intellectual culture along with the system of analyzing theological subjects – which was popularly used in Zoroastrian theology – can be found in such Zoroastrian works as the Dinkard, Bundahishn, and the Shikand-Gumanic Vichār. The similarity of belief pointed out by Ash’ari in his book, the “Al-Abānah”, as per which both the Mo’tazilites as well as the Zoroastrians hold man responsible for all evil actions and attribute all good to God proves the influence of Iranian culture and its impact on the Mo’tazilite theology. In his book, the “Surah al-Arz”, Ibn Huqal has mentioned that even the common people of Khuzestān – like the people of the other parts of Iran – widely discussed issues of theological importance. Moreover, Ibn Khaldun, too, in the introduction to his discussion claiming that “most Islamic Scholars are from among the Iranians” has spoken of the role of the Iranian culture and scholars in Islamic culture, emphasizing that even if rare cases of the emergence of some Arab scholars have been found, those scholars, too, have either been brought up in Iran or have been under the tutelage of Iranian scholars.It is important at this point to note that during the Sassanid period, Ctesiphon was the capital of Iran, and Iraq was regarded as the central province of the Iranian Empire and was popularly referred to as the “heart of the Iranian land”. Baghdad, Kufa, and Basra, too, had emerged from this central province under the influence of the Iranian culture and, both, the Mo’tazilites and the Ashā’erah theological schools had emerged from Basra. Iranian thoughts were spread in Basra by the Iranians who were referred to as “mawālis” and who lived in that region alongside the Arabs. During those times, Basra had inherited the interdependence that existed between the Iraq region and Khorāsan and the Indian subcontinent and was regarded as the administrative center of the eastern part of the Islamic territories. The genealogy of a number of the Basran thinkers, including theologians, could be traced back to the Asāvareh (Asvārān) clan that comprised a group of Iranians who had been living in Basra for a long time, in the same manner as the Ahāmareh (Bani al-Ahmar), which was another Iranian clan that had settled down in Kufa. The Asāvareh spoke in Persian and the Mo’tazelite theologians of Basra, too, were apparently well-versed with the Persian language. For instance, Nezzām Mo’tazeli was well-versed with the meanings of Persian proper nouns while Abu al-Hazil ‘Allāf is known to have referred derogatively to Abu Bakr Asam as “kharbān” (meaning “donkey-keeper”). Moreover, Musā bin Sayyār Asvāri who was one of the first theologians of Basra gave lessons in the exegesis of the Glorious Quran, both, in the Persian as well as the Arabic languages. These instances vividly reveal the presence of the Iranian culture and the Persian language in the territories that were the birthplace of various theological schools and their branches.It appears that the people of Iraq were originally Persian-speaking and that the Arabic language had only gradually come to replace Persian in this land. For instance, history has recorded that Mokhtār Saqafi’s troops mainly comprised the mawālis of Kufa who were Iranian Muslims who had settled in Kufa, and when he was defeated, contrary to his earlier claims promising victory, the mawālis have been reported to have remarked to each other in Persian, in the words “in bār dorugh goft”, meaning “he lied this time”.Needless to say, the spread of the Persian language in Iraq - which was the birth-place of Islamic theology - is indicative of the presence of Iranian thought in this land and its impact on the emerging theological thoughts to which we earlier referred to as the influence of the intellectual culture that had existed in Iran under the Sassanid rule. This phase of the evolution of theology has been classified under the following two periods:A) The Anti-Iran PeriodB) The Pro-Iranian Period